This invention relates to a method of withdrawing liquid from a reservoir, such as a concentrate container, by means of a water jet device received in a clamping device, this reservoir having an outlet opening fitted with a valve mechanism provided with a lip seal, while further on the one hand a water supply hose connects to the water jet device and on the other hand a drain spout.
In a similar method disclosed in German Offenlegungsschrift 36 07 623, a container made of synthetic plastics is provided with lips having hook shaped ends arranged for coaction with complementary openings of the clamping device to which the said water jet device has been previously attached.